1. Field
The present application relates to a substrate for an organic electronic device, an organic electronic device, a method of preparing the device or the substrate, and a lighting apparatus.
2. Related Art
An organic electronic device (OED) is a device including at least one organic material layer which is capable of conducting a current. Types of organic electronic devices include an organic light-emitting device (OLED), an organic solar cell, an organic photo-conductor (OPC) and an organic transistor.
An organic light-emitting device, which is a representative organic electronic device, usually includes a base layer, a first electrode layer, an organic layer and a second electrode layer in this order.
In a structure known as a bottom-emitting device, the first electrode layer may be formed as a transparent electrode layer, and the second electrode layer may be formed as a reflective electrode layer. In a structure known as a top-emitting device, the first electrode layer may be formed as a reflective electrode layer, and the second electrode layer may be formed as a transparent electrode layer.
Electrons and holes injected by the electrode layers are recombined in a light-emitting layer in the organic layer to produce photons. The photons may be emitted toward the substrate in the case of the bottom-emitting device, whereas the photons may be emitted toward the second electrode layer in the case of the top-emitting device. Refractive indexes of indium tin oxide (ITO), which is conventionally used as the transparent electrode layer, the organic layer and the base layer, which is conventionally a glass, are approximately 2.0, 1.8 or 1.5, respectively, in the organic light-emitting device structure. Due to the relation of these refractive indexes, for example, the photons produced in the light-emitting layer of the bottom-emitting device may be trapped by a total internal reflection in an interface between the organic layer and the first electrode layer or in the base layer, and therefore only a very small amount of photons is emitted.
Another important issue to be considered in the organic light-emitting device is durability. Since the organic layer or the electrode layer may be very easily oxidized by foreign substances, such as moisture and oxygen, it is important to secure the durability against environmental factors. For this issue, for example, U.S. Pat. Nos. 6,226,890 and 6,808,828, and Japanese Patent Laid-open Publication Nos. 2000-145627 and 2001-252505 suggested the structure which may block the introduction of foreign substances.